This project in concerned with 1) obtaining a detailed description of vocal behavior of squirrel monkeys, with emphasis on the use of specific call types and vocal exchanges associated with affiliative behavior; 2) analyzing the developmental course of vocal behavior by serial recording during growth of laboratory-reared infants; 3) recording and classifying vocal output during various sterotyped species-typical behavior patterns such as mating, genital display, and juvenile play. Studies begun during the previous year on changes in vocal behavior during estrous cycling have been completed and we are now looking at vocal usage during the birth and early dependency periods in stable social groups. Detailed description of the unusual vocal components of male genital display should be completed within FY82.